The series 2400 vinyl sliding window has a fusion welded vinyl frame and sash which creates strong, weathertight corners. Dual weatherstripping virtually eliminates drafts. Durable rollers and a specially designed rolling track make opening and closing these windows easy. Integral nailing fin can be removed for replacement applications. Low E3 glass is insulated with argon gas to reduce heat loss. Color matched cam action pack. U-factor is 0.29. Limited lifetime warranty. White.